Inhibition of phospholipase A2 activity by S-nitroso-cysteine in a cyclic GMP-independent manner in PC12 cells

Abstract Arachidonic acid and nitric oxide (NO) act as retrograde and intercellular messengers in the nervous system. Regulation of cyclooxygenase is well established, but regulation of phospholipase A 2 , the enzyme responsible for the liberation of arachidonic acid, by NO has not been thoroughly investigated. Using the PC12 cell line as a neuronal model, we studied the effects of exogenous NO compounds on arachidonic acid release. Incubation with Ca 2+ ionophores or mastoparan (wasp venom peptide) stimulated [ 3 H]arachidonic acid release from prelabeled PC12 cells. [ 3 H]Arachidonic acid release was inhibited by cytosolic phospholipase A 2 inhibitors, but not by dithiothreitol. A cytosolic phospholipase A 2 protein band with a molecular mass of ∼100 kDa was detected by immunoblotting. S -Nitroso-cysteine inhibited basal and stimulated [ 3 H]arachidonic acid release in concentration-dependent manners. Other NO compounds such as sodium nitroprusside and S -nitroso- N -acetylpenicillamine did not affect [ 3 H]arachidonic acid release. N -Ethylmaleimide also inhibited [ 3 H]arachidonic acid release. The inhibitory effects of S -nitroso-cysteine and N -ethylmaleimide were irreversible, because [ 3 H]arachidonic acid release from PC12 cells preincubated with S -nitroso-cysteine or N -ethylmaleimide was much lower than that from nontreated cells. These findings suggest (a) cytosolic phospholipase A 2 is activated by Ca 2+ or mastoparan, and inhibited by S -nitroso-cysteine in a cyclic GMP-independent manner, (b) N -ethylmaleimide also inhibits cytosolic phospholipase A 2 and arachidonic acid release in PC12 cells. S -Nitroso-cysteine can regulate the production of other retrograde messenger arachidonic acid.